Mobile networks are currently evolving from pure circuit switched (CS) networks towards packet switched (PS) networks, in particular Internet Protocol (IP)-based networks, and by that integrate into IP based infrastructures that are also used for the Internet, the World Wide Web, and the datacom industry.
More specifically, technologies allowing voice communication over an IP-based network have been introduced to mobile communication networks. Examples of such mobile networks are mobile networks as specified by the 3rd Generation Partnership Project (3GPP). For example, a mobile communications network may implement an IP Multimedia Subsystem (IMS) as specified in 3GPP Technical Specification (TS) 23.228 (e.g. version V13.2.0; 2015—) and offer voice and/or video communication as an IMS service provided over a packet data session. Sometimes, the packet data session is also referred to as a bearer.
Traditionally, the IMS provided IP-based multimedia functionality to CS networks. Recently, IP-based multimedia functionality is also provided over PS networks. An example is to employ the IMS to offer voice and video call functionality over the 3GPP Evolve Packet Core (EPC) system using different kind of accesses, which comprise: the—so called—“3GPP access” types (e.g. such as accesses provided by Long Term Evolution, LTE, radio access technology, RAT; sometimes referred also as 4G access), as well as the—so called—“non-3GPP accesses” (e.g. such as WiFi accesses). The communication services provided by the (multi-access type) telecommunications systems cited above allow the users subscribed to any of these system to establish packet data sessions through them that—among other, but not limited to—allows voice communication services. Therefore, a common expression utilized by 3GPP specifications is railed “Voice over LTE”, VoLTE; although, as commented above, the kind of access utilized by the user (subscriber) from her terminal to connect to the telecommunications systems can vary (e.g. 3GPP access types, and non-3GPP access types).
Deployment of VoLTE requires significant efforts from the operators to migrate a subscriber from a legacy CS service to a VoLTE service. Specifically, an access point node of the IMS network needs to be identified by a correct setting of an access point name (APN) at the terminal of a user associated with a subscriber that seeks to access certain IMS network to establish the corresponding packet data session. E.g., the IMS network to which access is sought for may belong to the operator said user is subscribed. The packet data session may then be routed towards the corresponding IMS network.
When migrating from legacy CS service to VoLTE service, it is possible that misconfiguration occurs. E.g., wrong APN(s) may be specified, either or both: in the terminal of a subscriber, or in certain nodes of the telecommunications network. Similar problems arise where a terminal of a subscriber seeks to access any kind of PS-network different to the IMS.